This invention relates to phased array antennas, and in particular to means for implementing limited scan operation of that type of antenna with microwave circuitry.
Conventional phased arrays are seldom proposed as antennas for high-gain, limited-scan applications because their required element spacings are small, and the resulting number of elements and phase shifters is excessively large. It has long been recognized, however, that if flat-topped radiation patterns could be synthesized to suppress the grating lobes, arrays of relatively few but larger sub-arrays or elements could be used for these applications. Although several element design approaches have met with reasonable success, allowing spacings up to 0.9.lambda., much larger spacings would be achievable if overlapped sub-array distribution could be produced.
This approach has in the past been neglected because of the lack of microwave circuits that are capable of effectively achieving the required overlapped sub-array distribution. THe present invention is directed toward providing microwave circuitry and element coupling arrangements that will permit the use of such an approach.